Products (such as computers, electronic components, power systems, batteries and other related products) are often located in hostile environments and may be exposed to excessively hot temperatures. Specifically, for example, when a battery is exposed to temperatures beyond its designed upper limit, the battery will fail. Battery manufacturers often direct customers not to expose batteries to temperatures above their limits and will nullify warranty coverage in cases where the battery is exposed to excessive heat. Nevertheless, there is no inexpensive way for the battery manufacturer to readily ascertain and prove to a customer with convincing evidence when a battery has failed due to exposure to excessive temperatures.
Typically, temperature sensor devices, such as thermocouples and thermisters, are used in outdoor power systems to provide feedback control for voltage or current regulation of battery charging system. Such sensors, however, are commonly placed directly on the battery case or battery post to measure the battery temperature, not the ambient temperature. Since the battery temperature can become higher than the ambient temperature surrounding the battery, it is not possible for a sensor on the battery case or post to measure the atmospheric temperature that the battery is exposed to.
Additionally, such temperature sensor devices measure temperature instantaneously, when in fact, it may take several minutes or even hours of exposure to ambient temperatures above the upper limit of a battery, before it will fail. Moreover, thermocouple and thermister devices do not typically store temperature levels and respective exposure times, due to excessive costs associated with manufacturing such a system. So the battery manufacturer has no permanent sensor device to indicate whether a battery had been exposed to ambient temperatures beyond its upper limit for a period of time long enough to damage the battery.
What is needed, therefore, is an inexpensive and permanent temperature detector that clearly indicates whether a battery has been exposed to excessive temperatures for a period of time beyond the design limit of the battery.